Development of Hard-Tissue Substitute by Superplastic Deformation of Carbonate Apatite

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In recent years, calcium phosphates have been used as biomaterials. We previously reported that sintered carbonate apatite has higher biocompatibility than hydroxyapatite and β-TCP, and can be widely applicable as biomaterials such as bone filling and replacement materials. Carbonate apatite ceramics also shows marked plastic deformation at high temperatures. To use carbonate apatite as hard tissue substitution materials with arbitary shapes utilizing this high plastic deformability, basic evaluation of the conditions for the development of plastic deformation (superplastic deformation) and the amount of deformation was performed in this study. Sintered carbonate apatites were placed in an electric furnace attached to a Survopulser (Shimazu Co.). Pressure was applied via an alumina fixture at 0.2 Kn until the specimen was heated to a designated temperature. Thereafter the preasure was increased to 10 Mpa as an initial load. The linear dimension of the carbonate apatite specimen was mea … More sured for 2hr, and the behavior of plastic deformation was examined. After the deformation, SEM and X-ray diffraction analysis of samples were performed, and changes in their physical properties were evaluated. As a result, when the initial load was 10 Mpa, slight plastic deformation occurred at 700℃. The amount of plastic deformation linearly increased with an increased in holding temperature, reaching about 80% at 800℃. When viewed with SEM, the specimens appeared to be composed of larger grains after the deformation. Considerable porosity were present in specimen before the load application, but the porosity decreased after the load application. X-ray diffraction analysis revealed the improvement in crystallinity after the deformation and a slight degree of crystal orientations. These results suggested improvement in physical properties after the deformation. Thus, sintered carbonate apatite has superplasticity at a comparatively low temperature. Thesefore, if appropriate load, temperature, and time are evaluated for the superplastic deformability, sintered carbonate apatite with various shape can be used as hard tissue substitution materials Less